EXTEENAL CHAEACTEES, HABITS AXD
Configuration. — The (ribbons are the smallest Anthropoid Apes, the largest being only a little more than three feet long from the crown to the heels. They are also slenderly built, so the total mass of the body
is small. The arms are longer in proportion to the length of the body than in all other Apes, and they touch the ground when the animals are fully erect ; their span is very great, that in a Siarnang three feet long being 5i feet. The forearm is longer than the arm, and the hand is longer than the foot as in the Chimpanzee ; and the mode of life of these animals has earned the
name of " Brachiators " for them. "Weber (162) points out that the great length of the arms is a*post-embryonal development. The tail is absent, and the small gluteal regions have callosities; in the possession of these structures the Gibbons resemble the Monkeys and differ from the other Apes.
Hand.—The hand is long and narrow. The skin of
the palm is glabrous and pigmented ; in the Siamang,
Bornean and Hainan Gibbons it is black, but it is paler
in the Hoolock Gibbon. The relative lengths of the